The present invention relates to a method and apparatus of treating sewage, by bacteria digestion with oxygen supplied by electrolysis.
The treatment of sewage by bacteria which attacks and breaks down the constituents of the sewage is well known. Such bacteria is usually oxygen-dependent so that there must be supplied to the plant oxygen in some form. In a number of installations, the oxygen has been supplied by the introduction of air into the compartment in which the bacteria acts upon the sewage, known as a digester. It has also been suggested in some instances that oxygen be supplied be electrolysis of the water constituent of the sewage.
Where electrolysis has been used for the supply of oxygen to the bacteria which digests the sewage sludge, the anodes and cathodes of the electrolysis system have been placed generally in the same tank, so that escaping hydrogen and oxygen gases, from the sludge, were free to reunite. This resulted in a fire and explosion hazard, where these gases were permitted to evolve from the surface of the sludge into a space above the sludge, and beneath a cover. In other embodiments, there was no cover for the digester compartment, so that the gases were permitted to escape, haphazardly, into the atmosphere.
In another proposal, the electrolysis took place in high pressure electrolytic units, which generated hydrogen and oxygen, and which gases were fed under pressure through a pressure engine, and thence into separate storage tanks. This proposal required substantial equipment for handling and storing gases under high pressure, and was therefore expensive to construct.
Sewage treatment plants as presently proposed are intended for handling the sewage of relatively large populations, but there is, also, a need for the treatment of sewage generated by communities having smaller populations, as are sometimes found on, for example, smaller military installations. The known sewage treatment plants require substantial treatment facilities, including relatively large peripheral and support equipment. Also, effluent from sewage treatment plants has not been as clean as desirable, thereby making the provision of discharge of the effluent difficult to achieve, and restricted to a relatively few methods. Further, the effluents from known plants provide the danger of contamination to the environment, as well as certain unsightliness in the effluent disposal.